MARSHFIELD — Construction has begun on a solar array in Marshfield that officials expect will provide two-thirds of the power needed at the town’s Old Schoolhouse Common.

Town Clerk Bobbi Brimblecombe said Friday that installation of the three-unit array should be completed in a week and will be operational when Green Mountain Power connects to it after that. The building houses the town clerk’s office, the Jaquith Public Library and the Twin Valley Senior Center.

The array will track the sun’s movements to increase efficiency and will be directly behind the Old Schoolhouse Common on the hillside.

Brimblecombe said the whole project cost $97,020 for installation, plus the cost of Green Mountain Power tapping in. The town received $33,960 from the Vermont Small Scale Renewable Energy Incentive Program to pay for the project.

The remaining balance of $63,060 will be paid by the town. At a special town meeting in October residents approved the spending of up to $65,000 on the project, which will cover the balance of the installation and Green Mountain Power’s services.

Brimblecombe said the panels will pay for themselves in 12 years and will save the town some money for the eight years after that. She said the town’s property tax rate will be higher for the next five years to pay for the investment, but the rate will then be lower than it otherwise would for 15 years thereafter. The town also has some money set aside for other projects that it will draw upon for this project.

In a memo on the project, the town said it expects the solar array to produce 67 percent of the electricity the Old Schoolhouse Common currently uses. Brimblecombe said that if electric use in the building can be reduced to the point where the solar array is producing more than the building needs, Green Mountain Power will give the town a credit toward the cost of electricity for other town buildings.

Brimblecombe said the point of the project was not necessarily to save the town money. She said the point was also to reduce the town’s carbon footprint to help combat climate change.

The solar panels themselves are guaranteed to operate without maintenance for 25 years, Brimblecombe said, and other parts of the installation are under warranty for 10 to 20 years.